arXiv subjects

Mohammad Hossein Koohi Ghamsari

Publications and source records attributed to Mohammad Hossein Koohi Ghamsari.

6 recordsLinked to original sources

arXiv2026

Reconfigurable Intelligent Surfaces: Architectures, Models, and Applications

Reconfigurable Intelligent Surfaces (RIS), also known as programmable metasurfaces, have emerged as a promising technology for next-generation wireless communication systems by enabling programmable control over the propagation environment. Through dynamic manipulation of the phase, amplitude, and polarization of electromagnetic waves, RIS introduces new degrees of freedom for enhancing coverage, spectral efficiency, energy efficiency, and interference management. This article reviews recent advances in RIS-enabled wireless communications, focusing on RIS architectures, emerging design and analysis techniques, and their impact on system-level performance. Key challenges related to scalability, hardware non-idealities, channel modeling, and control overhead are discussed, along with promising solutions and future research directions toward practical RIS deployment in beyond-5G and 6G networks.

eess.SY↗

arXiv2026

Circuit-Based Dispersion Analysis of Periodic Cross-Shaped Unit Cells with Dirac Characteristics

In this paper, the dispersion behavior of periodic cross-shaped unit cells is investigated with emphasis on Dirac-type dispersion using an equivalent circuit modeling approach. Two unit-cell geometries, including a simple cross structure and a modified configuration with a central patch, are analyzed using full-wave eigenmode simulations and scattering-parameter-based dispersion extraction. An equivalent circuit model is developed to capture the dominant coupling mechanisms and accurately reproduce the dispersion characteristics near the $Γ$-point. The results demonstrate that the proposed circuit model exhibits good agreement with full-wave simulations and provides a physically intuitive framework for analyzing stopband behavior and mode degeneracy. Furthermore, the limitations of S-parameter-based dispersion extraction in the presence of low-Q radiative modes are highlighted.

eess.SY↗

arXiv2026

EEG-Based Motor Imagery BCI Algorithms and Technologies: A Review

Brain-computer interfaces (BCIs) have emerged as transformative technologies that enable direct communication between the brain and external devices. Among various BCI paradigms, EEG-based motor imagery (MI) has gained prominence due to its simplicity, non-invasiveness, and potential to restore motor function and facilitate rehabilitation for patients with motor impairments. This paper presents a comprehensive review of the most practical processing algorithms developed over the past decade for decoding brain sensorimotor cortex signals. Specifically, this paper discusses the integration of artificial intelligence (AI)-based algorithms, particularly machine learning and deep learning techniques, and their contributions to improving the performance and efficiency of MI-BCI systems in detail. Furthermore, the paper reviews state-of-the-art hardware platforms and emerging converging technologies, including system-on-chip (SoC) architectures, application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), wearable devices, the Internet of Things (IoT), and augmented/virtual reality (AR/VR), and discusses their integration with advanced signal processing algorithms to enable next-generation MI-BCI systems. By highlighting current achievements of EEG-based MI-BCI technology and predicting future research directions that could further enhance real-time capabilities, this paper aims to provide valuable insights for researchers and practitioners, fostering innovation in high-performance EEG-based MI-BCI systems.

eess.SP↗

arXiv2025

A Corrugated All-Metal Vivaldi Antenna for 5G Phased Array Applications

In this paper, a corrugated Vivaldi phased array antenna in the 28 GHz frequency band is proposed for 5G communication applications. The presented configuration features an all-metal antipodal antenna structure with a broad bandwidth ranging from 26 to 30 GHz and beam steering capabilities from -30 to +30 degrees. The proposed antenna consists of a 4x4 array configuration, where each element has dimensions of 6.46x6.46x14.25 mm, resulting in an overall antenna structure with dimensions of 25.84x25.84x14.25 mm. The corrugation method is applied to minimize surface currents, resulting in a reduction in interelement mutual couplings. Therefore, the return loss in the array structure for central elements is decreased, and the antenna gain and radiation efficiency are improved. Moreover, the improved radiation efficiency allows for higher power transmission and reception from an antenna, resulting in potentially higher data rates and better performance.

eess.SP↗

arXiv2025

Confocal Ellipsoidal Reflectors with Phased Array Vivaldi Antenna Source for Imaging Systems

In this paper, an on-axis dual-reflector confocal ellipsoidal structure is presented for near-field imaging systems. In the proposed structure, the backscattered electromagnetic wave problem, known as the blockage effect, is reduced considerably using an elaborate design of the sub-reflector and precise alignment of the reflectors. The proposed geometry is analyzed, followed by a design example for the stand-off distance of 2 m. The blockage reduction characteristic is verified using ray-tracing simulation. Next, the scanning performance of the structure is investigated utilizing a Vivaldi phased array antenna as the source designed at the central frequency of 28 GHz. The full-wave simulations proved a field-of-view (FoV) of approximately 40 cm. Furthermore, tuning the proposed reflectors configuration standoff distance is examined with a point source. The ray-tracing simulations showed that stand-off distance can be easily changed up to tens of centimeters with just a few centimeters of source point lateral displacement.

physics.optics↗

arXiv2021

Open-stub based spurious harmonic suppression method for Microstrip Coupled Line Filter

In this paper, first, we review a straightforward analytical technique based on image impedance concept for designing traditional microwave microstrip coupled line filters using distributed elements. In the introduced approach, we characterize a quarter-wave coupled line section, and then these discrete sections can be connected in series to synthesis the final desired frequency response. Next, we use a novel open-stub based technique to suppress spurious harmonic frequencies. Finally, using proposed technique, we design and simulate a band pass filter (BPF). The simulation results prove the usefulness of the proposed technique.

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